Decaborane derivatives



United States Patent 3,269,803 DECABORANE DERIVATIVES Daniel Grafstein, Morristown, and Jack Bobinski, Rockaway, N.J., assignors to Thiokol Chemical Corporation, Bristol, Pa., a corporation of Delaware No Drawing. Filed May 7, 1963, Ser. No. 278,785 8 Claims. (Cl. 23-358) The present invention relates to novel compounds containing boron and to methods for making the same.

In recent years, there has been considerable interest in boron-containing compounds because the high heat of combustion of these compounds adapts them for use as rocket fuels. According to the present invention, [boron compounds have been prepared, which compounds are useful as intermediates in the preparation of boroncontaining polymers useful as propellant binders. Moreover, the compounds of the present invention are themselves useful as high-energy fuels and as fuel additives. The solid products of this invention, either per se or after formation into a polymer, can be used as solid propellants for rocket power plants and other jet-propelled devices when mixed with suitable oxidizers such as ammonium, potassium, or sodium perchlorates, ammonium nitrate, etc. Such propellant mixtures are compounded by a number of techniques known to the art. For example, the mixtures may comprise from to 35 parts by weight of boron-containing materials and from 65 to 95 parts by weight of solid oxidizing agents mixed there with. In some cases the propellant may also be made by combining the boron compounds and oxidizers with a curable polymer, for example, of the polyethylene, polyurethane, polyester, or polyether types.

Other products of the invention may be used as additives in high-energy liquid fuels by mixing the products with combustible liquids such as compatible hydrocarbon fuels.

Furthermore, hydrazine and compounds incorporating the hydrazine radical have also been the subject of intense experimental work because of the low atomic weight of the constituent atoms of hydrazine and the potential energy contained therein, and the consequent desirability of hydrazine and its compounds as rocket-fuel additives which contribute large quantities of energy and gas to the propulsion system.

It is an object of this invention to provide energetic compounds comprising both borane and hydrazine constituents. It is another object of this invention to provide energetic fuels and fuel additives for reaction motors. It is a further object of this invention to provide processes for producing said energetic compounds. Other objects of this invention are in part obvious and in part pointed out hereinafter.

The products of the present invention are trihydrazine decaborane and dihydrazine decaborane having, respectively, the following formulae:

As written above, these formulae indicate the intramolecular electronic balance. The processes by which the products of the present invention are obtained include methods wherein a decaborane derivative which is more highly substituted with hydrazine than the desired product is destabilized to allow production of the dihydrazine-substituted or trihydrazine-substituted decaborane derivative.

In one embodiment of the present invention, hydrazine is reacted with a class of disubstituted-decaborane derivatives which are co-ordination compounds of a Lewis base with decaborane. This reaction takes place 3,269,803 Patented August 30, 1966 in acetonitrile solution and in the presence of water as follows:

N H +decaborane co-ondination compound 2 5' 2 z s) 1o 1o The substituted decaborane derivatives, which are useful for the embodiment of the invention being discussed, are co-ordination compounds of sulfur with decaborane, B H These co-ordination compounds are formed by the donation of electrons to the decaborane by the Lewis base. For example, the sulfur atom in idiethyl sulfide, which has the following electronic configuration is capable of donating electrons to form a covalent bond with a chemical which is electronically disposed to accept such electrons. This type of chemical combination is called co-ordinating, and the compounds 'found thereby are called co-ordination compounds. Decaborane is a suitable co-ordinating compound probably because the tricovalent nature of boron readily allows it to accept electrons available in molecules of diethyl sulfide. These electron-donating compounds are known in the chemical art as Lewis bases.

Compounds useful for the present invention are the dialkyl sulfides, and, preferred among such compounds is diethyl sulfide which forms a co-ordination compound with decaborane by the following reaction:

This reaction is suitably carried out in an inert solvent at room temperature. The .alkyl groups in the aforementioned compounds are preferably chosen from among lower alkyls (i.e. 14 carbon atoms), but may also be any higher alkyl groups which permit solubility of the co-ordination compound in the solvent chosen as the medium for the reaction.

Bis(idiethylsulfide)decaborane, the product of Reaction 1 above, is reacted with aqueous hydrazine and in acetonitrile solution. The reaction is as follows:

The product of the reaction is trihydrazine decaborane.

The Reaction 3 between hydrazine and bis(dialkylsulfide)decaborane proceeds suitably at room temperature (2030 C.), but is conveniently performed at temperatures below room temperature for ease in controlling reaction rate or maintaining volatile reactants or solvents in the convenient condensed form.

In all cases, the reactants are suitably maintained in contact for a time permitting substantially complete reaction. The reaction time is not critical, .and will vary with the reaction temperature, concentration, etc. as is usual in chemical reactions.

In other embodiments of the present invention, decaborane more highly substituted with hydrazine or hydrazinium radicals may be treated to produce lower hydrazine-substituted decaboranes. For example, tetrahydrazine decaborane may be dissolved in a polar liquid such as alcohol or Water. Upon recrystallization of the material, trihydrazine decaborane will appear as the recrystallized solid.

In the recrystallization process, the temperature at which tetrahydrazine decaborane is dissolved and recrystallized is not critical and will vary with the solubility of the material Within a given solvent system at different temperatures. The solvent utilized for this operation will preferably be a polar solvent such as ethyl alcohol, water, etc.

Furthermore, if a mole of tetrahydrazine decaborane is subjected to avacuum, one mole of hydrazine will be removed and the material will be converted into trihydrazine decaborane. Typically suitable conditions for this process are temperatures in the range of 20 to 75 C. and absolute pressures of from about 1 to mm. of Hg.

Another method for converting more highly substituted hydrazine decaboranes to the lower-substituted products is to react the former compounds with a strong acid like trifluoroacetic acid. In this reaction, each molecule of acid will combine with a molecule of hydrazine, which latter is removed from the hydrazine-decaborane compound. Thus, for example, tetrahydrazine decaborane when reacted with two moles of the acid is converted to dihydrazine decaborane, and is converted to trihydrazine decaborane when reacted with one mole of the acid.

The reaction of hydrazine-substituted decaboranes with a strong acid, resulting in the removal of hydrazine therefrom, may be carried out at room temperature, and is a convenient method of preparing the products of the present invention. Temperatures above room temperature may be used but care should be taken to avoid an exothermic heating to the decomposition temperature of the reactants. This reaction may proceed between the reactants directly or in solution in an organic solvent. Conventional aliphatic, cycloaliphatic, and aromatic hydrocarbon and oxygenated solvents such as benzene, toluene, ethyl alcohol, hexane, dioxane, and ethers can be employed as will be evident to the organic chemist.

Acids useful in this reaction are strong acids such as trifluoroacetic acid and tr-ichloroacetic acid. Other strong acids may be used effectively when they are chosen in such a way as to avoid side reactions with the solvent medium and the reactants.

In order to point out more fully the nature of the present invention, the following specific examples are given as illustrative embodiments of the present processes and products produced thereby.

Example 1 Three grams of bis(diethylsulfide)decaborane were dissolved in 50 ml. of acetonitrile. While this solution was maintained at a temperature below C., 2.7 ml. of aqueous hydrazine, containing 0.8 mole of hydrazine, were slowly added to the solution. As this addition proceeded, a solid formed in the mixture. The mixture was agitated for one hour following the completion of the hydrazine addition; during this period, the quantity of solid precipitate increased. The solid was then recovered by filtration and dried under vacuum. A product yield of 23%, based upon the theoretical-1y possible yield, was realized. The melting point of the trihydrazine decaborane product was 118120 C.

Example 2 One-half gram of tetrahydrazine decaborane was dissolved in 260 ml. of boiling ethyl alcohol. After cooling, the recrystallized material was recovered and identified as trihydrazine decaborane by infra-red analysis Calculated for N H B N, 38.83; H, 11.18; B, 49.97. Experimental percent: N, 39.04; H, 10.98; B, 49.97.

The melting point of this material was 119120 C. Product yield was 92% of that yield theoretically possible.

Example 3 A suspension of 2.49 grams of tetrahydrazine decaborane was prepared in 80 ml. of methyl alcohol. To this suspension 1.5 ml. of trifiuoroacetic acid, dissolved in 20 ml. of ethyl alcohol, were added. This addition was carried out with care taken to maintain the temperature of the mixture below 20 C. A clear solution resulted.

To a suspension of 0.84 gram of trihydrazine decaborane in m1. of methyl alcohol was added 0.38 gram of trifluoroacetic acid. Care was taken to keep the mixture at room temperature during the addition of the acid. The solid product, dihydrazinium decaborane, was isolated by fractional crystallization, and identified by infra-red analysis.

We claim:

1. A sol-id compound of the formula 2. A process for the removal of up to two molar parts of hydrazine from one molar part of tetrahydrazine decaborane which comprises dissolving the tetrahydrazine decaborane in an inert solvent medium, reacting therewith a molar quantity of a strong acid corresponding to the molar amount of hydrazine sought to be removed therefrom, and recovering the solid product of the reaction.

3. A process as in claim 2 wherein said strong acid is trifluoroacetic acid.

4. A process as in claim 2 wherein one molar part of tetrahydrazine decaborane is reacted with one molar part of strong acid to yield trihydrazine decaborane.

5. A process as in claim 2 wherein one molar part of tetrahydrazine decaborane is reacted with two molar parts of strong acid to yield dihydrazinium decaborane.

6. A process for the removal of up to one molar part of hydrazine from one molar part of trihydrazine decaborane which comprises dissolving the trihydrazine decaborane in an inert solvent medium, reacting therewith a molar quantity of a strong acid corresponding to the molar amount of hydrazine sought to be removed therefrom, and recovering the solid product of the reaction.

7. A process as in claim 6 wherein said strong acid is trifluoroacetic acid.

8. A process as in claim 7 wherein one molar part of trihydrazine decaborane is reacted with one molar part of strong acid to yield dihydrazinium decaborane.

References Cited by the Examiner UNITED STATES PATENTS 3,000,712 9/1961 Kilner 23-14 3,l=19,652 1/1964 Uchida 23-14 3,148,938 9/1964 Knoth 23190 XR 3,149,010 9/1964 Armstrong 23-190 XR 3,153,567 10/1964 Fetter 23-190 XR OTHER REFERENCES AEC Document, UCRL4332, April 19, 1954, p. 12.

Carpenter, American Rocket Society Journal, January 1959, pp. 8 11.

Hurd, Chemistry of Hydrides, 1952, pp. 73-74.

Steindler et al., Journal of the American Chemical Society, vol. 75, p. 756, February 1953.

OSCAR R. VERTIZ, Primary Examiner.

CARL D. QUARFORTH, Examiner. J. D. VOIGHT, Assistant Examiner. 

1. A SOLID COMPOUND OF THE FORMULA
 2. A PROCESS FOR THE REMOVAL OF UP TO TWO MOLAR PARTS OF HYDRAZINE FROM ONE MOLAR PART OF TETRAHYDRAZINE DECABORANE WHICH COMPRISES DISSOLVING THE TETRAHYDRAZINE DECABORANE IN AN INERT SOLVENT MEDIUM, REACTING THEREWITH A MOLAR QUANTITY OF A STRONG ACID CORRESPONDING TO THE MOLAR AMOUNT OF HYDRAZINE SOUGHT TO BE REMOVED THEREFROM, AND RECOVERING THE SOLID PRODUCT OF THE REACTION. 